1. Field of Invention
The present invention relates to an optical component housing made of metal to hold optical components that constitute an optical system, and to a projection display device using the optical component housing.
2. Description of Related Art
Hitherto, a projection display device has been used which may consist of a light source, an optical unit for forming an optical unit by modulating a light beam emitted from the light source according to image information, and a projection lens for enlarging and projecting the modulated light beam onto a projection plane. The optical unit includes an illumination optical system for uniformizing the in-plane illumination distribution of a light beam emitted from the light source, a color separation optical system for separating the light beam from the illumination optical system into color beams of the primary colors, red, blue, and green, an optical modulation system for modulating the color beams according to image information, and a color synthesizing optical system for synthesizing the modulated color beams.
Optical components, such as dichroic mirrors for constituting the color separation optical system, and condenser lenses placed on the incident side of the optical modulation device, are usually housed in an optical component housing, called a "light guide", because they need to be precisely placed on the optical axis extending from the light source to the projection lens. The adoption of an optical component housing made of metal, such as a magnesium alloy, as such an optical component housing has been examined. When the optical component housing made of metal is adopted in the projection display device, since the strength of the material is high, it is reduced in thickness, thereby reducing the weight of the device. Since a metal having high thermal conductivity is adopted as the material, it is possible to improve efficiency in cooling various optical components housed therein.
In addition to molding methods, such as casting and forging, thixomolding is known as a method of producing the above-described optical component housing made of metal, in which injection molding is performed using semi-molten metal consisting of coexisting solid and liquid phases, by agitating the semi-molten metal and thereby lowering the viscosity thereof.
According to this thixomolding method, since an injected material can be molded at a lower temperature than in casting, such as die casting, less shrinkage occurs due to solidification by cooling, and it is easy to ensure dimensional accuracy. Moreover, since the surface of a molded article is close, it is possible to simplify subsequent processes such as buffing.